U.S. patent application number 12/744007 was filed with the patent office on 2010-12-16 for method of reservation with guarantee of latency and of bit rate in a time slot dynamic allocation network.
This patent application is currently assigned to THALES. Invention is credited to Domininique Heurguier.
Application Number | 20100318661 12/744007 |
Document ID | / |
Family ID | 39810304 |
Filed Date | 2010-12-16 |
United States Patent
Application |
20100318661 |
Kind Code |
A1 |
Heurguier; Domininique |
December 16, 2010 |
METHOD OF RESERVATION WITH GUARANTEE OF LATENCY AND OF BIT RATE IN
A TIME SLOT DYNAMIC ALLOCATION NETWORK
Abstract
A resource reservation method with guaranteed service in terms
of minimum bit rate and maximum access time at radio network nodes
using time slots each associated with an individual bit rate for
sending and transmitting data. A node includes a protocol layer
that sends a reservation request to a MAC layer. The source node
introduces into the format of the Path and Resv messages of the
RSVP protocol fields corresponding to the maximum duration of the
time slot observed on the current path in the Adspec reservation
request of the Path message, the number of radio nodes crossed in
the object of the Path message, and the maximum waiting time for
the time slot in the Rspec object of the Resv message corresponding
to the response to the reservation request. The MAC layer reserves
the number of time slots needed to satisfy the service guarantee
recorded in the reservation request.
Inventors: |
Heurguier; Domininique; (Le
Perreux Sur Marne, FR) |
Correspondence
Address: |
STROOCK & STROOCK & LAVAN LLP
180 MAIDEN LANE
NEW YORK
NY
10038
US
|
Assignee: |
THALES
Neuilly Sur Seine
FR
|
Family ID: |
39810304 |
Appl. No.: |
12/744007 |
Filed: |
November 24, 2008 |
PCT Filed: |
November 24, 2008 |
PCT NO: |
PCT/EP08/66083 |
371 Date: |
May 20, 2010 |
Current U.S.
Class: |
709/226 |
Current CPC
Class: |
H04W 28/26 20130101;
H04L 47/724 20130101; H04L 47/70 20130101; H04W 84/18 20130101;
H04L 47/824 20130101; H04W 72/087 20130101 |
Class at
Publication: |
709/226 |
International
Class: |
G06F 15/16 20060101
G06F015/16 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 23, 2007 |
FR |
07/08221 |
Claims
1. A resource reservation method with guaranteed service in terms
of minimum bit rate Dmin and maximum access time Amax at the N
nodes of a radio network using time slots Di each associated with
an individual bit rate Deli for sending and transmitting data, a
node of the network comprising a protocol layer and a MAC network
access layer, comprising the following steps: the protocol layer of
the node sends a reservation request to the MAC layer of the node;
the source node sending the data introduces into the format of the
Path and Resv messages of the RSVP protocol: a field Ts
corresponding to the maximum duration of the time slot observed on
the current path in the Adspec reservation request of the Path
message, transmitted from the source node to a recipient; a field n
concerning the number of radio nodes crossed in the object of the
Path message; a field .tau. giving the maximum waiting time for the
time slot in the Rspec object of the Resv message corresponding to
the response to the reservation request sent by the recipient to
the source node; and the MAC layer of said node reserves the number
of time slots Di needed to satisfy the service guarantee recorded
in the reservation request.
2. The method as claimed in claim 1, further comprising the steps
of implementing a dynamic time slot allocation method for the
sessions, then a reservation of the MAC packets for the sessions on
the reserved time slots D.sub.i by dynamically adapting the size of
the MAC packets to the need of the application.
3. The method as claimed in claim 1, wherein the RSVP reservation
request is then declined in the MAC layer as follows: Maximum
transmission delay required: .tau.'=m'.Ts Minimum bit rate
required: R' in which Ts corresponds to the duration of a slot and
m' to the number of packets reserved.
4. The method as claimed in claim 1, wherein the network is an ad
hoc radio network, and a radio frame includes four layered
elements: a basic MAC resource, a time "slot", a basic frame BF, a
frame F, a frame comprising a control slot allocated to a given
node transmitting the MAC level signaling, several time slots
intended for transmitting elastic data or session packets.
5. The method as claimed in claim 1, wherein the method uses a
periodic TDMA at each node.
6. The method as claimed in claim 1, wherein the method is used to
modify the format of the messages used in the OPWA mode.
7. The method as claimed in claim 1, wherein the method uses an IP
protocol.
8. A network comprising a source node, a recipient node and one or
more intermediate nodes, the source node including sending means,
Ei, for sending a resource reservation request, the recipient node
including means for receiving this request and sending in turn a
path reservation message, and the nodes using time slots to send
and transmit data, wherein each intermediate node includes a MAC
layer and a protocol layer, wherein the protocol layer of the node
sends a reservation request to the MAC layer of the node; the
source node sending the data introduces into the format of the Path
and Resv messages of the RSVP protocol: a field Ts corresponding to
the maximum duration of the time slot observed on the current path
in the Adspec reservation request of the Path message, transmitted
from the source node to a recipient; a field n concerning the
number of radio nodes crossed in the object of the Path message; a
field .tau. giving the maximum waiting time for the time slot in
the Rspec object of the Resv message corresponding to the response
to the reservation request sent by the recipient to the source
node; and the MAC layer of said node reserves the number of time
slots Di needed to satisfy the service guarantee recorded in the
reservation request.
9. The network as claimed in claim 8, wherein the network is an ad
hoc network.
10. The method as claimed in claim 2, wherein the method is used to
modify the format of the messages used in the OPWA mode.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the U.S. National Phase application
under 35 U.S.C. .sctn.371 of International Application No.
PCT/EP2008/066083, filed Nov. 24, 2008, and claims the benefit of
French Patent Application No. 0708221, filed Nov. 23, 2007, all of
which are incorporated by reference herein. The International
Application was published on May 28, 2009 as WO 2009/065958.
FIELD OF THE INVENTION
[0002] The invention relates to ad hoc radio networks with time
division multiple access TFDMA. It targets more particularly the
resource reservation capability including the end-to-end bit rate
and latency constraints, one or other of these constraints
potentially predominating. An ad hoc network is defined as a
network in which the constituent nodes are mobile, that is to say
that the number of nodes in the network is likely to change over
time.
[0003] It also applies to multiple-channel systems with time and
frequency division multiple access, TDMA, the radio networks using
an OFDMA (Orthogonal Frequency Division Multiple Access) orthogonal
frequency modulation, and to any other system which uses a dynamic
allocation scheme instead of a fixed allocation scheme.
[0004] For information, in the description, the following messages
and objects of the RSVP protocol are used: [0005] the Tspec object
of the PATH message describes the application's traffic profile,
[0006] the Adspec object describes, among other things, the
characteristics of the path and in particular the maximum bandwidth
available on the path, [0007] the Rspec object of the RESV
reservation message contains the bandwidth to be reserved for the
data stream.
[0008] The sender sends a PATH message to a recipient to which data
must be transmitted, the recipient or receiver responds by sending
a reservation message RESV containing the bandwidth to be reserved
for the routers via which the message or data packets are
relayed.
BACKGROUND OF THE INVENTION
[0009] The TDMA radio networks generally use static allocations.
The allocation is either totally fixed (cyclical frame with one
slot for each node), or predefined for a given configuration.
[0010] The new radio systems are beginning to take account of
service quality, but they do not yet support overall resource
reservation with guaranteed service from end-to-end in terms of bit
rate and latency. For example, they do not support the service
guarantee over IP (Internet Protocol) protocols such as the
"Reservation Protocol services" resource reservation protocol,
better known by the abbreviation RSVP.
[0011] Regarding resource reservation, the current radio systems
known to the Applicant with time division multiple access like TDMA
cannot guarantee both the minimum bit rate and a maximum latency
from end-to-end.
[0012] A recent method described in the Patent Application FR 06
11279 filed by the Applicant and entitled "Method for reserving and
dynamically allocating time slots in a network with guaranteed
service" applies the RSVP protocol to a TDMA network with the
following implementation restrictions: medium access control MAC
packets of fixed size for the sessions and a reservation adapted to
the applications with latency constraints predominating over bit
rate constraints. In practice, this method does not make it
possible to optimize resource consumption and is uneconomical,
particularly for applications with predominant bit rate
constraints.
[0013] The invention relates to a medium access control MAC level
method for dynamically allocating radio resource time slots, better
know as slots, with session packets or packets reserved for a
session in an application, having a variable size and a service
guarantee, that can be used equally in applications requiring a
predominant latency constraint and/or a predominant bit rate
constraint to be observed. Two types of traffic are differentiated:
elastic traffic and session traffic. Session traffic corresponds,
for example, to continuous multimedia streams (voice and video) and
real-time data streams for which a strong service guarantee (bit
rate and latency) is desired. Elastic traffic corresponds, for
example, to a file transfer.
SUMMARY OF THE INVENTION
[0014] The present invention is based notably on the invention
described in the Patent Application FR 06 11279 mentioned
previously which makes it possible to implement dynamic session
slot allocations locally, that is to say without recourse to
centralized management in normal operation. The method described in
this prior art is based on an explicit assignment of the session
"slots" to one or more nodes and on a concept of reservation of
these "slots". A "slot" assigned to a node can be freely reserved
by this node to satisfy a resource reservation request. As seen
from a given node, the set of unreserved session "slots" forms a
group or pool of resources from which the node can potentially
draw.
[0015] In the case of an application with predominant latency
constraint, the method described in the Patent Application FR 06
11279 makes it possible to decline an overall reservation from
end-to-end with guaranteed latency, of RSVP type in latency
management mode, better known by the abbreviation OPWA, standing
for "One Pass With Advertising", in the MAC layer when a slot
consists of a number NPS of MAC packets of fixed size.
[0016] In this case, the parameters C and D of the Adspec message
have the values:
C=BR.Ts/NPS=size of an MAC packet
D=additional transmission time
With the following MAC parameters (partly defined previously): BR:
bit rate of the TDMA channel, N: number of network nodes, K: number
of physical slots for a node, NPS: number of MAC packets per
physical slot, H: number of physical slots taken by the node
concerned, Ts: duration of a physical slot, m: number of MAC
packets reserved.
[0017] The RSVP request is then declined in the MAC layer as
follows: [0018] maximum transmission delay required: .tau.=C/R
[0019] minimum bit rate required: R=r
[0020] The present invention uses a novel approach which comprises
a reservation of the variable size session packets, the size of a
session packet being defined notably by the maximum size of a
packet of the application, plus the MAC level encapsulation data
such as the header, and the explicit management of radio access
delay at the reservation protocol level.
[0021] In an embodiment, the invention relates to a resource
reservation method with guaranteed service in terms of minimum bit
rate Dmin and maximum access time Amax at the n nodes crossed in a
radio network using time slots or slots Di each associated with an
individual bit rate Deli for sending and transmitting data, a node
of the network comprising a protocol layer and an MAC network
access layer, characterized in that it comprises at least the
following steps:
for a given node, the protocol layer of said node sends a
reservation request to the MAC layer of said node, the source node
sending the data introduces into the format of the PATH and RESV
messages of the RSVP protocol: [0022] a field Ts corresponding to
the maximum duration of the time slot observed on the current path
in the Adspec reservation request of the PATH message, transmitted
from the source to a recipient, [0023] a field n concerning the
number of radio nodes crossed in the Adspec object of the PATH
message, [0024] a field .tau. giving the maximum waiting time for
the time slot in the Rspec object of the RESV message corresponding
to the response to the PATH reservation request sent by the
recipient to the source node, [0025] the MAC layer of said node
reserves the number of time slots Di needed to satisfy the service
guarantee recorded in the reservation request.
BRIEF DESCRIPTION OF DRAWINGS
[0026] Other features and advantages of the present invention will
become better apparent from reading the following description of an
example given as a nonlimiting illustration, with appended figures
which represent:
[0027] FIG. 1, the principle of resource reservation,
[0028] FIGS. 2A and 2B, a frame format and a time slot in the case
of a TDMA single-source application, and
[0029] FIG. 3, the exchanges between the IP and MAC TDMA layers,
for the example given.
DETAILED DESCRIPTION OF THE INVENTION
[0030] In order to better understand the principle implemented in
the method according to the invention, the description is given as
an illustration and is by no means limiting, for a TDMA ad hoc
radio network in which all the nodes are independent and can play
the same role. A node 1 will act as the source at a given instant,
a second node 2, the recipient of the message or of the data, and a
number of intermediate nodes 3i. For this, all the nodes (source
node and recipient nodes) are each equipped with a processor Pi
suitable for implementing the steps of the method according to the
invention. They are also provided with radio means, sender and
receiver Ei, Ri, with which to transmit the messages to other nodes
and receive messages from these other nodes, the recipient node has
means for receiving this request and sending in turn a path
reservation message, the nodes using time slots to send and
transmit data. An intermediate node comprises an MAC layer and a
protocol layer and means for implementing the method according to
the invention. Such equipment is known to those skilled in the art
and will not be described in detail. A few reminders are given for
the terminology used and the context of the invention in the
preamble to the explanation of the method and of the system
according to the invention.
Terminology
[0031] The architecture of a radio frame consists of 4 layered
elements which will convey the useful data, a useful data unit
potentially being a packet of the application, for example an IP
packet: [0032] Individual MAC resource: MAC packet (encapsulation
packet at the MAC level of an application packet), [0033] Time
slot: better known by the term "slot", [0034] Basic frame: BF,
[0035] Frame: F
[0036] These various elements are detailed hereinbelow.
MAC Packet
[0037] The MAC packet is a basic data structure at the MAC level.
It has a variable size. For a given session, its size is fixed and
is determined by the maximum size of an application packet.
Time Slot, Basic Frame and Frame
[0038] The basic frame and the "slots" are illustrated in FIGS. 2A
and 2B
Cn: control slot for the node n Di: slot of the basic frame (other
than the control slot) Ts: slot duration K: number of slots making
up the basic frame T.sub.BF: duration of the basic frame with
T.sub.BF=K*Ts
[0039] Each basic frame contains K slots. The first slot Cn.sub.0
in each basic frame is called "control slot". This is a "fixed
slot" permanently allocated to the node n.
[0040] The slots can be divided into three classes: [0041] The
control slots Cni used to transmit the MAC level signaling
(signaling packets needed for the operation of the MAC level
services such as discovery of neighbors and frame synchronization).
These services and their implementation are known to those skilled
in the art and will not be detailed again. [0042] The "elastic"
slots used to transmit the elastic data: generally a subset K of Di
slots (in which i=1 . . . K-1) are allocated statistically to
nodes, in order to transmit elastic data. Thus, Dij, (in which j=1
. . . P) slots are reserved for the transmission of elastic data
(each node thus having P slots evenly distributed in the frame).
Hereto, the term "elastic" is a term usually known to those skilled
in the art and unambiguously designates data. [0043] The "session"
slots used to transmit session packets. These slots can support
elastic data. They are reserved for a given session.
[0044] If the control slot Cni and the elastic slots Dij are
counted, the N.(K-1-P) remaining slots in the overall frame
constitute session slots which can be dynamically allocated so as
to transmit the session packets. The unassigned session slots are
grouped together in a set or pool and are divided up between all
the nodes of the network. This means that any node that needs to
satisfy a required service quality can use one or more slots from
the set or pool.
[0045] A slot "Di" (in which i=1 . . . . K-1) of the overall frame
can be assigned permanently to a node (elastic slot), temporarily
(session slot allocated to a node or to several nodes in a space
reuse case), or form part of the pool of available session
slots.
[0046] There are as many basic frames as there are nodes in the
network. The frame F consists of all the basic frames. If the
network is formed by N nodes, the frame F structure consists of N
basic frames BF. The duration T.sub.F of the frame has the value
T.sub.F=N*T.sub.BF=N*K*Ts.
Resource Reservation Request and Allocation of Session Slots
[0047] The "pool" of the session slots consists of a maximum of
N*(K-1-P) slots. Each slot can potentially use any session slot
from the pool, whereas the control slot and the elastic slots are
definitively allocated to a node.
[0048] With a new session, the MAC layer 5i of a node 3i (FIG. 3)
receives a resource reservation request Res(Dmin, Amax) (broken
line arrow in the figure) matched with a minimum bit rate
constraint Dmin and a maximum slot Di access delay constraint Amax.
The resource reservation request is sent from the protocol layer,
in the example, the IP protocol (FIG. 3).
[0049] Each slot Di is characterized by an associated individual
bit rate Deli. A node Ni can thus assess the number of slots Di
that it needs to satisfy the reservation request in terms of bit
rate Dmin based on the individual bit rate Deli offered by a slot
Di.
[0050] It is the medium access layer MAC that effectively allocates
the resources corresponding to a resource reservation request for a
session. For a given node, this MAC layer chooses the session slots
Di of the frame F needed to satisfy the resource reservation
request and then, the MAC layer starts appropriate negotiation
procedures to reserve the slots belonging to the pool. The MAC
layer starts its procedures according to a principle disclosed in
the Applicant's Patent Application FR 06 11279. It then reserves,
in the allocated slots, the space needed for the MAC packets, that
is to say that the method reserves a space corresponding to a
number of MAC packets, one slot being able to support a number of
MAC packets. The size of an MAC packet is determined by the maximum
size of a packet of the application supported by the session, the
session being open to the profit of an application. The maximum
size is specified in the Tspec object of the Path message.
[0051] A number of constraints are taken into account in the slot
and MAC packet allocation algorithm: [0052] the resources allocated
must be compatible with the minimum bit rate Dmin requirements
specified in the reservation request, [0053] the maximum slot
access delay Amax must be compatible with the maximum delay imposed
in the reservation request. Declension of an Overall Resource
Reservation, of RSVP type, in the MAC Layer
[0054] In order to support the resource reservation request at the
MAC level, two parameters are introduced into the MAC request:
[0055] .tau.: the maximum delay required to access a slot,
[0056] R: the minimum bit rate required.
[0057] These two parameters are used in the resource allocation
algorithm, so as to guarantee that the reservation request with
service guarantee is observed.
[0058] In the case of a periodic TDMA at each node, the Resv
message for the RSVP resource request is reflected in the MAC layer
by a reservation in terms of number of MAC packets. The RSVP
parameters are described according to the IETF's RFC specifications
known to those skilled in the art and will not therefore be
explained in this patent application.
[0059] For example, the parameters used to describe the envelope of
the traffic according to the token bucket model are, according to
the "token bucket" recommendation RFC 2212 available via the link
http://www.faqs.org/rfcs/rfc2212.html. [0060] p=peak rate
(octets/sec) [0061] b=bucket capacity ("bucket depth") (octets)
[0062] r=token bucket rate (octets/sec) [0063] m=minimum policed
unit (octets) [0064] M=maximum size of the application's data
packets ("maximum datagram size") (octets).
[0065] The transmission delays for each node Ni are described by
the following two parameters: [0066] C.sub.i=rate dependent factor
(octets) [0067] D.sub.i=rate independent term (sec)
[0068] Thus, the limit on the transmission delay for a packet at a
minimum rate R for the node Ni is:
.tau..sub.i=C.sub.i/R+D.sub.i
[0069] In the case of a TDMA protocol with slots that are totally
periodic at each node, the RSVP calculation method can be used by
establishing a strict correlation between the MAC parameters and
the RSVP parameters.
[0070] The mathematical relations between the parameters C.sub.i
and D.sub.i of the field corresponding to the message of the path
that the data will use for the RSVP AdSpec protocol (the PATH
message of the RSVP protocol) and MAC level parameters described
previously are then as follows: [0071] C.sub.i: size of an MAC
packet (octets) [0072] D.sub.i: possible additional delay
associated with slot management or with the processing and internal
transit of an MAC packet.
[0073] For identical nodes, the parameters are independent of the
node and no longer need to be indexed.
[0074] Note that the relation for the parameter Ci or C is strictly
valid only if the allocation leads to a substantially uniform time
distribution of the physical slots of each node within the overall
frame and if the MAC packets of one and the same session are
divided up over distinct physical slots.
[0075] The method considers MAC packets of variable size. For a
given session, still with predominant latency constraint, the size
of the MAC packets reserved will be set to the value M of the
maximum application packet size supported.
[0076] In this case, when the slots are decoded globally, the
parameters of the "Adspec" resource reservation message C and D
corresponding to the respective packet size and possible additional
delay associated with slot management or with processing and
internal transit of an MAC packet parameters then have the
values:
C=M maximum packet size
D=Ts+Do
[0077] With Do being the possible additional transmission time.
[0078] The bit rate consumed at the MAC level for the encapsulation
of the packets has not been taken into account in the interests of
simplification. To include this encapsulation would amount to
considering R to be the useful bit rate for the application.
[0079] If we now consider the general case of a session with dual
latency and bit rate constraint, without assuming that the latency
constraint is predominant, the declension of "RSVP OPWA", based on
an equivalence between latency and bit rate, becomes unsuitable for
the applications with predominant bit rate constraint, for which it
introduces excessive maximum slot access delay constraints.
[0080] In practice, for example, an RSVP request with non-existent
latency constraint should be declined in the MAC layer as follows:
[0081] Maximum transmission delay required: .tau.=infinity [0082]
Minimum bit rate required: R=r
[0083] To process the resource reservation with guaranteed bit rate
and latency appropriately for applications for which the
predominant constraint is not, a priori, known, or in the case in
point, if the latency constraint is low, the method should be able
to separately manage the latency and bit rate characteristics. It
is then possible to consider an extension of the OPWA mode of the
RSVP protocol by adding the following fields: [0084] a field Ts
corresponding to the slot duration in the AdSpec object of the
resource reservation message, [0085] a field n concerning the
number of radio nodes crossed in the AdSpec object of the resource
reservation message, [0086] a field .tau. giving the maximum
waiting time for the slot in the Rspec object of the response
message to the resource reservation message Resv.
[0087] Considering the maximum latency from end-to-end .delta., and
the maximum slot waiting time .tau. at each node, the following
mathematical relations are established:
In the case where the guaranteed bit rate is less than the peak bit
rate R.ltoreq.p:
.delta. = ( b - M ) ( p - R ) R ( p - r ) + M R + i = 1 n ' D i + n
.tau. ##EQU00001##
in which n' is the total number of nodes on the path, possibly
greater than the number n of radio nodes on the path given
previously.
[0088] In the case where the guaranteed bit rate R is greater than
the peak bit rate p, R.gtoreq.p:
.delta. = M R + i = 1 n ' D i + n .tau. ##EQU00002##
[0089] The maximum slot access delay has the value:
.tau.=T=m.Ts [0090] m being a non-zero integer and Ts the duration
of a slot.
[0091] The reservation optimization problem is then expressed:
[0092] Max m [0093] Min R
[0094] In which the maximization of m is considered to take
priority over the minimization of the bit rate R subject to the
following constraints:
.delta. ( R , .tau. ) .ltoreq. .delta. max ##EQU00003## R .gtoreq.
r ##EQU00003.2## R .ltoreq. R max ##EQU00003.3## R .gtoreq. M .tau.
+ T s ##EQU00003.4## .tau. = m T s ##EQU00003.5##
[0095] In which Rmax is the maximum acceptable bit rate and
.delta.max the maximum end-to-end latency constraint.
[0096] The solution for the optimum (R, m') is written:
if Rmax.ltoreq.p:
[0097] m ' = min ( .delta. max - i = 1 n ' D i - M R max - ( b - M
) ( p - R max ) R max ( p - r ) n T s , N . K ) R ' = max ( r , ( b
- M p - r ) p + M .delta. max - i = 1 n D i - n m ' T s + b - M p -
r ) ##EQU00004##
if Rmax.gtoreq.p:
[0098] m ' = min ( .delta. max - i = 1 n D i - M R max n T s , N K
) ##EQU00005## R ' = max ( r , M .delta. max - i = 1 n D i - n m '
T s ) ##EQU00005.2##
[0099] The RSVP reservation request is then declined in the MAC
layer as follows: [0100] maximum transmission delay required:
.tau.'=m'.Ts with m' being the number of packets reserved [0101]
minimum bit rate required: R'
[0102] In various embodiments, the invention notably offers one or
more of the following advantages: [0103] optimizing the allocation
of the resources for the sessions by reserving session data packets
of appropriate size, [0104] guaranteeing a service quality at the
node level on the session streams in terms of bit rate,
transmission delay and jitter, [0105] making it possible to put in
place application service guarantees at the level of the higher
layers, in terms of minimum bit rate and maximum latency value for
the end-to-end application. These guarantees can be applied to
applications with predominant latency constraint but also to
applications with predominant bit rate constraint. This is then
done by implementing an overall reservation mechanism derived from
the RSVP standard protocol, by enriching the "OPWA" mode.
* * * * *
References